Fat Soluble Vitamins: D, E & K

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the active form of vitamin D known as?

Cholecalciferol

Calcitriol (correct)

Calciferol

25-hydroxycholecalciferol

Which organ is primarily responsible for the activation of vitamin D into its active form?

Intestine

Liver

Skin

Kidney (correct)

Which protein is 25-hydroxycholecalciferol bound to in plasma?

Albumin

Calcium binding protein

Globulin

Vitamin D binding protein (VDBP) (correct)

What stimulates the activation of 1α-hydroxylation of vitamin D?

Parathyroid hormone Signup and view all the answers

Which vitamin D metabolite is primarily responsible for increasing intestinal absorption of calcium and phosphorus?

Calcitriol Signup and view all the answers

What effect does low doses of calcitriol have on bone?

Promotes bone formation Signup and view all the answers

How many hydroxyl groups does calcitriol contain?

3 Signup and view all the answers

At high doses, which metabolite of vitamin D may promote bone resorption?

24,25-dihydroxycholecalciferol Signup and view all the answers

What is the role of the vitamin D receptor (VDR) in gene expression?

It binds to retinoic acid X receptor (RXR) to regulate gene expression. Signup and view all the answers

Which of the following is a specific function of vitamin D?

Stimulating expression of calcium binding protein Signup and view all the answers

What is a primary function of alpha-tocopherol, the most active form of vitamin E?

It acts as a natural anti-oxidant. Signup and view all the answers

How does vitamin E protect against aging?

By preventing the peroxidation of lipids. Signup and view all the answers

What is the relationship between selenium and vitamin E?

Selenium reduces the dietary requirement of vitamin E. Signup and view all the answers

In which cellular process does vitamin E act as a cofactor?

Electron transfer system of mitochondria Signup and view all the answers

What is the consequence of vitamin E’s antioxidant properties on red blood cells?

Protection from hemolysis Signup and view all the answers

Which function is NOT associated with vitamin D?

Enhancing glucose metabolism Signup and view all the answers

What is the primary function of Vitamin K in the body?

Synthesis of blood clotting factors Signup and view all the answers

Which vitamin K derivative is known to have a 20C side chain?

Phylloquinone Signup and view all the answers

How do warfarin and dicoumarol inhibit blood clotting?

By competing with vitamin K for carboxylation processes Signup and view all the answers

What role does osteocalcin play in the human body?

Promoting bone mineralization Signup and view all the answers

Which structural protein is specifically formed in osteoblasts and interacts with hydroxyapatite?

Osteocalcin Signup and view all the answers

Which of the following best describes the function of Vitamin K in mitochondria?

Electron transport and oxidative phosphorylation Signup and view all the answers

What is the role of the methyl group at C2 in Vitamin K?

It contributes to the activity of the vitamin Signup and view all the answers

Which vitamin is necessary for the synthesis of osteocalcin?

Vitamin D3 Signup and view all the answers

Which vitamin is formed from 7-dehydrocholesterol in the skin upon exposure to UV rays?

Vitamin D3 Signup and view all the answers

What is the primary animal source of Vitamin D3?

Egg yolk Signup and view all the answers

What is a poor source of Vitamin D3?

Milk Signup and view all the answers

Which compound can be converted into Vitamin D2 through UV exposure?

Ergosterol Signup and view all the answers

What distinguishes ergosterol from 7-dehydrocholesterol?

An extra methyl group in its side chain Signup and view all the answers

What is the primary reason ergosterol is not considered a significant dietary source of Vitamin D?

It is poorly absorbed in the intestines. Signup and view all the answers

Which vitamin can be commercially produced by exposing ergosterol to UV light?

Vitamin D2 Signup and view all the answers

What is a principal function of Vitamin D?

Calcium homeostasis Signup and view all the answers

Study Notes

Fat Soluble Vitamins 2: Vitamins D, E & K

Vitamin D (Cholecalciferol): Two types naturally occur:
- Vitamin D2 (Ergocalciferol): Provitamin is ergosterol. Sources include yeast, mushrooms, or plants contaminated by fungi.
- Vitamin D3 (Cholecalciferol): Provitamin is 7-dehydrocholesterol. Sources are animal-based, including fatty fish (tuna, mackerel, salmon), cod liver oil, egg yolk, and beef liver.
Vitamin D Formation:
- Vitamin D3: Formed in the skin when exposed to UV rays. Dietary sources are less prominent for obtaining adequate amounts of Vitamin D3.
- Vitamin D2: Can be formed in the skin by UV exposure of ergosterol.
Vitamin D Structure:
- Ergosterol differs from 7-dehydrocholesterol by a side chain: Vitamin D2 (ergocalciferol) has an unsaturated side chain while Vitamin D3 has a saturated side chain.
- UV radiation cleaves the B ring of both compounds, producing active Vitamin D.
Vitamin D Metabolism & Actions:
- Metabolism: Cholecalciferol is activated by the liver and kidneys into its active form, 1,25-dihydroxycholecalciferol (calcitriol), which is crucial for calcium and phosphorus absorption.
- Action: 1,25-dihydroxycholecalciferol (calcitriol) has critical roles in maintaining bone health, calcium regulation, and intestinal absorption of calcium and phosphorus. It promotes bone formation at low doses and bone resorption at high doses.

Vitamin E

Structure: Four main naturally occurring types: α, β, γ, δ tocopherols. α-tocopherol is the most potent.
Functions:
- Antioxidant: Crucial lipid-phase antioxidant.
- RBC Protection: Protects red blood cells from hemolysis.
- Cell Protection: Preserves cell structure and function from oxidative damage.
- Vitamin A & Carotenoid Protection: Protects these compounds from destruction due to free radicals.
- Aging: Reduces the effects of aging due to oxidative damage.
- Immune function: Boosts the immune response.
- Energy Production: Essential cofactor in mitochondrial electron transfer systems.
- Fertility: Crucial for fertility in some animal species.
- Selenium: Working in conjunction with selenium, it enhances the absorption of vitamin E.

Vitamin K

Structure:
- Vitamin K1 (Phylloquinone): Has a 20-carbon side chain.
- Vitamin K2 (Menaquinone): Has a 30-carbon side chain.
- Vitamin K3 (Menadione): Synthetic form.
Functions:
- Blood Clotting Factors: Necessary for synthesizing blood clotting factors II, VII, IX, and X in the liver.
- Gamma Carboxylation: Vitamin K is essential for the gamma carboxylation of glutamic acid residues for blood clotting factors.
- Calcium Binding: Carboxylated glutamic acid residues facilitate calcium binding, crucial for blood clotting.
- Anticoagulants: Warfarin and dicoumarol are anticoagulants; they inhibit vitamin K carboxylation due to structural similarities with vitamin K.
- Bone Health: Crucial in the binding of calcium and phosphate in the bone matrix, regulating bone mineralization, and synthesis of osteocalcin.
- Electron Transport: Involved in electron transport and oxidative phosphorylation. Important for ATP formation.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Dive into the intricate details of fat-soluble vitamins, focusing on Vitamins D, E, and K. Learn about the sources, formation, and metabolism of Vitamin D, including the differences between D2 and D3. This quiz covers essential knowledge for students of nutrition and health sciences.